While service companies have provided men, materials and money for development of continuous shear wave generators, there has been a paucity of similar efforts with regard to impulse shear wave generators. Furthermore, experience now shows that exploration situations do exist where a small portable shear wave generator could be quite useful, for example, for shallow bore hole velocity surveys or for shallow reflection/refraction activities involving small survey parties.
Available impulse generators of which were are aware involve a wide spectrum of equipment to provide shear wave energy, for use of shaped explosive dynamite charges and the like in selective field layouts, to use of large hammer-anvil apparatus in which a large rotational rim is positioned on a cable and is hurled through a wide arc to strike an anvil attached to the earth's surface.